Costa enjoyed an explosive start to his career at Stamford Bridge with nine goals in seven matches. But his progress has stalled due to a hamstring injury that has kept him out of Chelsea's last three matches including the Blues' visit to Manchester United on Sunday, which ended in a 1-1 draw.

While the 26-year-old landed in hospital due to a cold in the build-up to the match against United, Mourinho has revealed that it was Costa's hamstring injury rather than the virus that kept him out of the tie.

Blame

For that, the Chelsea boss has laid the blame for the ex-Atletico Madrid man's injury woes squarely on del Bosque, who deployed Costa in back-to-back Euro 2016 qualifiers against Slovakia and Luxembourg at the start of the month.

Mourinho said: "The virus is fine. It was hard, he had to go to the hospital and obviously it doesn't help him to recover from his injury.